Minimum radius for Aristo 3-axle motor units...?

[Zerogee]

The big Aristo diesels like the SD45 and Dash-9, which have the three-axle motor bogies, all seem to specify a minimum curve DIAMETER of 8 feet, ie: 4 foot radius; now this is just a LITTLE bit larger than LGB R3 - so will these motor units negotiate R3 track or not?
Is the minimum radius in this case limited solely by the amount of sideways play in the centre axle of each bogie, or by the amount of swing of the two bogies in the loco frame - or a combination of both?
My reason for asking, prompted by seeing a couple of the motor blocks up for sale, was this: could an 0-6-0 loco built on just one of these 3-axle motor units get round an R3 curve without binding?

Jon.

 

[Tony]

Hi Jon a lot depends on the track laying all the Aristo Deisels i have had will do R3s if the track is flat but introduce a dip or change of height and you could find it climbing out of the rails......I sold all my Class 66s because at the time my track wasnt that flat and most of the time they were fine but sometimes would come off...you can tell how tight they are if you try and put one on the track on a curve....having said that the biggest problem is with the Throw ???? if thats the right word of the units to each other in other words how much the pair will swival in relation to each other in the body and often you are on the limit of a rad 3.........not finished yet next is the couplings on some stock the overhang is so great that the couplings cant cope with the overhang and it gets worse if the coupling is body mounted
In short yes they will do R3s but some combinations may have problems

A quick word on steam locos....They seem to cope better.... my Mallet (Aristo) was perfect and although felt tight on bends never came to any grief but does look stupid on a R3 as the cab overhangs the track so much................I have a pair of Mikados and they also are fine but will visably slow down on a r3 and its because its a tad tight but they do have 4 driving axcles

Tony

 

[Neil Robinson]

A quick word on steam locos....They seem to cope better.... my Mallet (Aristo) was perfect and although felt tight on bends never came to any grief but does look stupid on a R3 as the cab overhangs the track so much................I have a pair of Mikados and they also are fine but will visably slow down on a r3 and its because its a tad tight but they do have 4 driving axcles
Tony

Aristo have a reputation for indifferent wheelset gauge that can vary from model to model and is nigh on impossible to adjust without the sort of tools found in a well equipped model engineering workshop. One problem in some cases is the wheel profile, if the back to back gauge is set correctly to negotiate pointwork check rails the wheels are wide to track gauge and, vice versa, if the track gauge is O.K. the flanges may foul check rails.
Take a look about three quarters of the way down this link. Don't get too despondent though, many Aristo locos perform well, but it's good to be aware of the potential problems to help sort out a loco if it misbehaves.

http://elmassian.com/trains/motive-power-mods-aamp-tips/aristo-motive-power/prime-mover-basics < Link To http://elmassian.com/trai...wer/prime-mover-basics

 

[ntpntpntp]

I have no problems with my SD-45 nor my class 66 on LGB R3 (which is my minimum radius). I've also had a couple of visiting 66s round my line with no problems. The class 66 is more restricted than the SD-45 because with the 66 the motor blocks are constrained more by the chassis frames. There was quite a discussion on this on the old GSM forum when the 66 came out. I took these photos at the time...

Here's a 66 on R3 (with R1 and R5 either side)

Here's a 66 upside-down with R3

Whilst I have no problems on my line, I have taken mine to a couple of other lines and it is true that R3 really is the limit for the 66. If you have any "slightly dodgy" track-laying (dog-legs, open joints, sudden changes in the camber) then it may climb the curve. The SD-45 seems to cope better as it has more play.

Jon, those two motor blocks you've seen for sale wouldn't be the pair on ebay per chance? I confess I put an opening bid on those but only in case no-one else goes for them (handy spares): I don't really need them and won't be chasing them. I notice the seller doesn't know how to track-test them by linking the inner and outer contact strips.

 

[steve parberry]

I think also they are very subject to nice track as above.

I remeber that we had issues with one Class 66 on the East Midlands layout even though the curve diameter was greater as an average, the curve was not uniform and caused a great deal of frustation.....

When we checked and realined, then the problems went away even though we had slightly tightend the radius.

Can't remember what the radius is but i am sure it is slightly bigger the LGB 3..

 

[dutchelm]

We have had an SD45 around my line which has a section of R2. the only problem with the loco was a scratch on the fuel tank where it fouled the fence.

 

[beavercreek]

The SD 45 blocks will negotiate R3 with no problems as long as the track geometry is fine.The loco might look uncomfortable and a bit out of whack but as long as extra clearance for the over-swing is present, then nothing untoward will occur.

The Aristo mallet has each powered axle being able to rock to overcome any track geometry problems.
Interestingly USA train designed one of the end axles on each 3 axle power bogie to be able to swivel independently to overcome any problems and this works well but can also lead to problems on very uneven track.

 

[Zerogee]

I have no problems with my SD-45 nor my class 66 on LGB R3 (which is my minimum radius). I've also had a couple of visiting 66s round my line with no problems. The class 66 is more restricted than the SD-45 because with the 66 the motor blocks are constrained more by the chassis frames. There was quite a discussion on this on the old GSM forum when the 66 came out. I took these photos at the time...

......

Whilst I have no problems on my line, I have taken mine to a couple of other lines and it is true that R3 really is the limit for the 66. If you have any "slightly dodgy" track-laying (dog-legs, open joints, sudden changes in the camber) then it may climb the curve. The SD-45 seems to cope better as it has more play.

Jon, those two motor blocks you've seen for sale wouldn't be the pair on ebay per chance? I confess I put an opening bid on those but only in case no-one else goes for them (handy spares): I don't really need them and won't be chasing them. I notice the seller doesn't know how to track-test them by linking the inner and outer contact strips.

Yes Nick, it was that pair that started the train of thought (pun intended!) though there is also a single one on German eBay that I spotted around the same time. It was mostly idle curiosity really, like you I haven't got anything specific to use them on - and from the other answers on this thread so far (thanks everyone, by the way) it probably wouldn't be a good idea anyhow - when I finally get my line down, though I'm trying to use R3 or larger almost everywhere, I do have one area where R2 may be unavoidable.

Thanks all!

Jon.